Experimental and numerical analysis of seasonal solar‐energy storage in buildings

This paper presents seasonal‐energy storage of solar energy for the heating of buildings. We distinguish several types of seasonal storage, such as latent, sensible, and chemical storage, among which the thermochemical storage is used and analysed in this research. In the first part, a laboratory heat‐storage tank, which was made in the laboratory for heating, sanitary, and solar technology and air conditioning from the Faculty of Mechanical Engineering, University of Ljubljana, Slovenia, was presented. The experimental model was tested for charging and discharging mode. Two types of numerical models for sorption thermal‐energy storage exist, which are microscale and macroscale (integral). For microscale analysis, the analysis system (ANSYS) model can be used to simulate the behaviour in the adsorption reactor. On macroscale or integral scale, TRaNsient SYStem (TRNSYS) model was used to perform the operation of the storages on the yearly basis. In the second part the simulation of the underfloor heating system operation with a built‐in storage tank was carried out for two locations, Ljubljana and Portoro?. Furthermore, the comparison between a thermochemical and sensible‐heat storage was performed with TRNSYS and Excel software. In this comparison, the focus was on the surface parameters of the SCs and volume of the thermal‐storage tank for the coverage of the energy demand for selected building. With this analysis, we would like to show the advantage of the thermochemical storage system, to provide greater coverage of the energy demand for the operation of the building, compared with the seasonal sensible‐heat storage (SSHS). Such a heat‐storage technology could, in the future, be a key contributor to the more environmentally friendly and more sustainable way of delivering energy needs for buildings.     

Stufenweise Elutionsanalyse thermisch dispergierter Stärken

Stepwise Elution Analysis of Thermically Dispersed Starches. Qualitative changes of kernels of sorghum, wheat, maize and potato starch and decomposition of their pastes during thermic dispersing at 120°C were observed by elution analysis. After thermic dispersing potato and sorghum starch were the most decomposed. The chromatograms of their pastes showed after thermic dispersing in water at smaller concentrations of perchloric acid new zones of the iodine starch complex. Due to the molecular decomposition the intensity of the coloured zones decreased in the lower and middle part of the chromatogram, while new zones with increased colour intensity appear in the upper parts. The chromatograms of all native starches showed more coloured zones than their pastes. This is in good correlation with previous determinations where all investigated native starches showed smaller average molecular weights than their corresponding pastes.     

Alkalizahlen thermisch dispergierter Stärken

Alkali Numbers of Thermically Dispersed Starches. The alkali numbers of six native starches and their pastes were determined by a potentiometric method. Analogous experiments were carried out with thermically dispersed starches. All investigated native starches showed higher alkali numbers than their pastes. Prolonged thermical dispersion lead to different increasing of the alkali numbers, probably due to a different velocity of thermic degradation in the starch molecules. A good correlation was observed between the reciprocal alkali numbers of thermically dispersed starches and their molecular weights.     

Tailor‐made Polymeric Membranes based on Segmented Block Copolymers for CO2 Separation

This paper reports the design of a tailor made polymeric membrane by using poly(ethylene oxide)–poly(butylene terephthalate) (PEO‐PBT) multi‐block copolymers. Their properties are controlled by the fraction of the PEO phase and its molecular weight. To explain the effect of structural changes in copolymer membranes, transport properties of four gases (CO₂, H₂, N₂, and CH₄) are discussed. After characterization, the two best copolymers are selected in order to prepare tailor made blends by adding poly(ethylene glycol) (PEG). The best selected copolymer that contained 55 wt. % of 4000 g mol⁻¹ PEO produced a blend with high CO₂ permeability (∼190 barrer), which is twice the permeability of the pure copolymer. At the same time, an enhancement of CO₂/H₂ selectivity is observed (∼13). These results suggest that the morphology of PEO‐PBT can be well controlled by the addition of low‐molecular‐weight PEG, and consequently the gas transport properties can be tuned.     

Wet‐phase‐separation membranes from the polysulfone/N,N‐dimethylacetamide/water ternary system: The formation and elements of their structure and properties

Asymmetric and porous polysulfone (PSf) membranes were prepared by wet phase separation. Binary (PSf)/N,N‐dimethylacetamide (DMA) solutions with polymer concentrations of 12.5–30 wt % were cast in thicknesses of 80–700 μm and immersed in a coagulation bath of pure water. The morphology of the formed membranes' cross sections consisted of a cellular structure and macrovoids; the cellular structure density was highest when the cast solution contained about 21 wt % PSf, regardless of the cast thickness. The membranes' pure water permeability decreased as the cast thickness increased. The instantaneous onset of the turbidity, regardless of the PSf content and cast thickness, its steep growth, and relatively high end value were the main characteristics of the turbidity phenomena taking place during the formation of the protomembranes. Again, the membrane‐forming system with a PSf/DMA solution with about 21 wt % polymer, regardless of the cast thickness, had the highest turbidity end value. The shrinkage of the cast solutions into the corresponding protomembrane was also examined quantitatively. Inverse experiments showed that the direction of the gravitation field had no influence on the shrinkage of the membrane‐forming ternary system or the membranes' morphology and its water permeability. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1667–1674, 2005     

Stufenweise Elutionsanalyse elektrodialysierter Fraktionen von Wachsmais- und Amylosestärke

Stepwise Elution Analysis of Electrodialysed Fractions of Waxy Corn- and Amylose Starch. Changes in the sol and gel fractions of waxy corn- and amylose starch during thermic dispersing were observed by stepwise elution analysis. The sol- and gel fractions were separated from pastes and dispersions, after being treated in an autoclave at 120°C, by electrodialysis. It was found that during the thermic dispersing the sol- and gel fractions of waxy corn paste decompose more intensively than the analogous fractions of amylose starch. Addition of alkali to the sol fraction of waxy corn- and amylose starch has no influence on the chromatograms. Especially in the gel fraction of amylose starch paste and partially also in the gel fraction of waxy corn starch paste fragments can be observed which after addition of alkali disaggregate. In the sol fraction of the paste of waxy corn starch only 9% of starch could be detected, in the sol fraction, isolated after 3 h of dispersing in an autoclave, however, 45% approx. were determined. In the analogous fractions of amylose starch no increase of the starch contents was observed.     

Thick suspension technology for fly ash transportation and disposal at a coal fired power plant

Modified technology for fly ash transportation and disposal was tested on a pilot plant at the “?o?tanj” Power Plant. The main advantage of this technology is in reduced water requirements for ash transportation and consequent smaller load on the environment with polluted water. The environmental impact of ash sludge deposited in this way was investigated and is described here.     

Thermo-Mechanical Analysis of Elasto-Plastic Cyclic Torsion of a Tubular Element

The paper treats a tubular element which presents a cantilever beam loaded by a torque moment on the free end. The value of torque is chosen so that the stresses range in the elasto-plastic domain. The rheological properties of the material follow the elastic-linear hardening model. The tubular element is subjected to a cyclic torsion of such frequency that heat is generated in the tubular element. The quantity of the generated heat depends on the amplitude of the torque, frequency of the load and mechanical properties of the tubular element material. The paper compares the results of the temperature change at characteristic points along the tubular element obtained via numerical analysis as well as experimentally.     

Polymeric membrane formation by wet-phase separation; turbidity and shrinkage phenomena as evidence for the elementary processes

The direct accumulation of polymer, the nucleation and growth of the polymer lean as well as the polymer rich phase and the spinodal phase separation are postulated as four elementary processes of the mechanisms of the polymeric membrane formation by wet-phase separation. With the study of five different polymer/solvent:water systems they are discriminated by the investigation of the turbidity and the shrinkage phenomena taking place during (proto)membrane formation, as well as by the measurement of the pure water permeability and by the inspection of the membranes’ cross-section morphology. The general scheme of membrane formation mechanisms is arranged by gathering the groups of different modes of mass transport and the group of nonsolvent/solvent/polymer forms of solidification as elementary processes; by forming combinations of the so postulated elementary processes in time and space particular mechanisms are established.     

Bewertung der Eigenschaften von Kartoffelstärken

Evaluation of Potato Starch Properties . Different potato starches were studied by determination of their consistency curves with a Brabender viscosigraph, their absolute viscosity values and the ranges of swelling temperatures of the starch grains. Gradual elution analyses for comparison were carried out, and a simple potentiometric method was introduced in order to determine the average number of molecular weights M_n. Between different potato starches essential differences of the physical and colloidalchemical properties could be revealed in spite of the fact that their quality corresponded to didacted standards. The physical and colloidal-chemical changes of the starches may be ascribed to prolonged or inadequate storage. At the evaluation of the starch qualities the existing standards are no longer satisfactory. The starches should be classified especially by viscographic measurements and determinations of the average number of molecular weigths.